The uses of vibratory conveyors, of various designs are well known. These devices have been employed in assorted industry segments for decades. One particular form of vibratory conveyor, that being, the excited frame vibratory conveyor, has found widespread usage in food processing and other industries. Excited frame conveyor construction, and their operation are well known. In most forms of the invention, a base frame which rests on or which is suspended from an underlying supporting surface mounts one, or more, out-of-balance electric motors, which rotate an eccentric weight in order to impart a vibratory force, which is directed along the given line of reference through the center of mass of the adjacent vibratory conveyor bed, this vibratory force causes the vibratory bed to reciprocate in a given direction by means of a multiplicity of leaf springs, which moveably support the conveyor bed on the base frame.
The aforementioned excited frame vibratory conveyors are extremely reliable and are convenient to use. Notwithstanding the high reliability of such excited frame conveyors, shortcomings in the operation of such devices have been the attention of designers, and the users of such devices, for many years. For example, designers of such excited frame conveyors have known, for some period of time, that as the conveyor bed length increases, certain resonant vibratory frequencies are generated as the conveyor bed begins to reciprocate following the energizing of these aforementioned, out-of-balance motors. These resonant vibratory frequencies, under certain conditions, can cause undesirable motion in the conveyor bed. These resonant frequencies become an increasing problem as the conveyor bed becomes longer. To avoid these resonance modes employing the aforementioned out-of-balance motors have entailed utilizing various schemes and methodology to energize out-of-balance motors in a predetermined manner so as to prevent these resonance modes from causing adverse side-to-side or twisting motions of the conveyor bed, about its longitudinal axis. These schemes have included so-called “ramp up” or “ramp down” energizing of the respective out-of-balance motors so as to minimize the resonance modes that are generated. Still further, the generation of these resonance modes, which causes adverse movement of the conveyor bed, especially at longer lengths, has caused another problem to arise, that being, the premature wear, or breakage of the leaf springs which support the conveyor bed on the base frame.
In addition to the foregoing, the use of out-of-balance motors employing eccentric weights has long known problems which are associated with the premature wear of bearings, which support the rotating shafts of the electric motors bearing the eccentric weights. As should be understood, and from time-to-time such out-of-balance motors need to be replaced due to excessive bearing wear. In addition to the foregoing, and when installed, the previously mentioned excited bed conveyors when installed, and rendered operable, utilize given eccentric weights, which provides a predetermined frequency of vibration for the accompanying conveyor bed. As should be understood, and depending upon the weight of the product being transported by the conveyor bed, adjustment of this vibratory force, which is imparted to the conveyor bed, is difficult to change, absent a replacement of the eccentric weights, which are rotated by the out-of-balance motor. Changing these weights takes some period of time to accomplish. Therefore, there is currently no convenient means to make both a frequency and amplitude change of the amount of force that an out-of-balance motor provides to a conveyor bed, absent significant revisions to the drive arrangement of such prior art excited frame conveyors. Further, for extremely long conveyors, and which may have multiple motors at given locations along the length of the conveyor bed, such conveyors employ a rather complex system to control these motors. Finally, the use of out-of-balance motors limits the designer to the use of a system, which employs merely a vibratory force, which is most accurately depicted as a sine-wave, and does not allow a designer to employ vibratory force, which may best be understood as being a complex wave form. Such a complex vibratory wave form may be useful for moving specific particulate matter along a given conveyor bed.
The present invention, as described hereinafter, avoids the detriments associated with the prior art practices utilized heretofore, and provides a new conveyor assembly for moving particulate product along a conveyor bed, in a particularly noteworthy manner.